基于尼罗河下游钻孔沉积物粒度端元分析的全新世流域水文气候变化

During the Holocene, the Nile River Basin experienced hydrological fluctuations that had a profound impact on the development of ancient Egyptian civilization. Understanding the paleo-hydroclimatic changes of the river basin is pivotal for the management of water resource and sustainable development of society. To illuminate the hydroclimatic variations and related drivers that have shaped the basin over the past ten millennia, we analyzed the end-member of grain size and their variation periodicity from core FA-1 in the Faiyum Basin and core B-1 in the delta. Results reveal that three distinct grain size end-members identified in the two cores are linked to their sedimentation and aeolian processes in the lower Nile basin. The vertical variations of the end-members signify a shift from a humid climate in the Early to Mid-Holocene to drier climate in the late Holocene. During the Late Holocene, the distinct hydrodynamic variations depicted by the sediment components of the two boreholes indicate that human activities notably influenced the local environment. Power spectral and wavelet analyses indicate that, at a centennial scale, the predominant periodicities of Holocene hydroclimatic fluctuations are approximately ~400, ~200, and 150 years. These align closely with the Indian Ocean monsoon cycles, underscoring the monsoon role in governing the hydrology of the Nile River basin. Furthermore, at a millennial scale, the periodicity of the Nile River discharge aligns with the changes in the Atlantic Meridional Overturning Circulation (AMOC), indicating the greater impact of the Atlantic moisture transport on the hydrology of the Nile River Basin. These findings provide a comprehensive chronicle of hydrological shifts in the river basin during the Holocene, delving into the intricate mechanisms that propel the changes, and offering new insights into hydroclimate variations of the Nile River Basin.